The invention relates to an undercarriage for a track-bound vehicle.
With the continuing increase in operational velocity, the undercarriages of modern track-bound vehicles must meet increasingly stringent requirements regarding stable running characteristics, good curve maneuverability with low horizontal force levels and low wear between the vehicle and the rail. These requirements are not met by conventional undercarriages where the individual wheel set axles are braced against the undercarriage with high longitudinal stiffness which, therefore, cannot execute the turning motions required for a radial adjustment of the wheel axle on a track curve, such as a tilting motion about the vertical axis.
For improving the maneuvering behavior of undercarriages on curves, the technique of suspending the individual wheel set axles rotatably in the undercarriage frame and adjusting the wheel sets forcibly as a function of the excursion angle of the undercarriage below the vehicle body radially to the track curve is known (see Swiss Pat. No. 183,368). Two steering linkages coupled to each other with positive motion transmission are provided for this purpose, each of which contains a reversing lever which is controlled at the vehicle body and is laterally supported at the undercarriage frame. The axle ends of the two-wheel set axles, each end overlying the same rail, are connected via a steering rod connected to the free level arm end and are adjustable in opposite directions in the longitudinal direction of the undercarriage. Such kinematic forced steering is dependent on the vehicle, body, in which the radial adjustment of the wheel set axles is derived from the relative rotation between the vehicle body and the undercarriage, and is not the subject of the present invention.
In undercarriages of the claimed type, such as cross-anchor undercarriages, the ability of automatic turning and guidance of the profiled rigid wheel set, which results on the one hand from lateral restoring forces geometrically related to the wheel/rail profile and, on the other hand, from force transmission due to slippage in the longitudinal and transverse direction, is utilized for the automatic radial adjustment of the wheel set in track curves in such a manner that the wheel set axles are guided at the undercarriage frame longitudinally elastically and are connected to each other in a self-adjusting manner with respect to their turning motions by a coupling device which is independent of the vehicle body (see DE-AS Nos. 23 56 267; 26 30 353; 26 31 350; European Pat. No. A-O, 161,729). For such a cross-anchor coupling of the respective diagonally opposite axle ends and wheel set bearings, respectively, however, the space in the center of the undercarriage which as a rule is not available in modern undercarriages, is required. Also, the lengthwise elastic axle springiness must be made so stiff for reasons of stability at higher speeds that the self-adjustment action of the wheel sets is substantially limited unless longitudinal dampers are provided in a structurally complicated manner between the undercarriage frame and the axle bearings, which then form, together with the transverse axle springiness via the undercarriage frame, a completely independent stability system. Finally, the longitudinal forces from the acceleration and deceleration of the track-bound vehicle are taken up via the longitudinal axle springs and exert a negative influence on the radial self-adjustment of the wheel sets in negotiating curves which can be avoided only by a further increase of the construction costs, namely, the incorporation of additional jointed levers which connect the wheel set axles approximately in the center of the axle to the undercarriage frame so as to transmit longitudinal forces but are free to turn.